Control for die pads, presses and the like



CONTROL FOR DIE PADS, PRESSES AND THE LIKE Filed Dec. 16, 1964 J. V.PERRONE Jan. 9, 1968 2 Sheets-Sheet 1 HTTOIZNEKS CRHIG QK mw m 3 9 Wm mn\ n\ NNQ ,\\N 5 M 8 f A m WV 1 MN Nu m YM B Nm 8 R B I a v N. S wvov IQM) a 7 w \u on v a n, wa 8 /g k 3 v a. 5 mm QR. to :0 \a. U5 m Jan. 9,1968 J. v. PERRONE 3,362,210

CONTROL FOR DIE PADS, PRESSES AND THE LIKE Filed Dec. 16, '1964 2Sheets-Sheet 2 nn \lk 4 9s 2 56-43 3: W V 7 M Q 25 22 Z4 34 A 92 31 5 27n n v) 28 L 76 38 K 32 15 INVENTOR.

l Jnnsj 1/. PERRONE 6 I? BY [vJlLjO/V, SETTLE & CRFIIG HTTQRNEKS UnitedStates Fatent G M 3,362,210 CONTROL FOR DIE PADS, PRESSES AND THE LIKEJames V. Perrone, 41 Shady Hollow, Dearborn, Mich. 48124 Filed Dec. 16,1964, Ser. No. 418,925 14 (Ilaims. (Cl. 72-351) ABSTRACT OF THEDISCLOSURE A control valve for regulating the flow of fluid between afluid source and a cylinder containing a fluid actuated piston. Thevalve includes a flow control mechanism to cushion the initial highpressure loadsresulting from extreme forces applied to the piston at thebeginning of a work stroke and a, hydraulically actuated combinationdelay and check valve assembly to delay the return of the piston to theextended position after the work stroke.

The present invention relates to a control mechanism for presses and thelike and more particularly to a simplified and improved cushioning anddelaying hydraulic control system for controlling the movement of a diepad to and from a working position in a press.

In modern, high speed presses commonly utilized for performing stamping,drawing or other operations upon sheet metal, it is necessary to providefor accurate, controlled movement of the die pad normally carrying thelower of the cooperating die elements of the press. The die padconventionally contacts at least one cylinder contained piston and ismovable with the piston. It has been previously proposed, for example,by US. Reissue Patent No. 25,027 and like developments, to provide ahydraulic system for controlled die pad movement consisting of anaccumulator and cylinder connected by a normally closed check andshutoff valve block and utilizing a separate normally closed by-passrelief valve block in parallel with the check and shutoff valve block.By this arrangement, two separate costly controlled hydraulic flow pathmechanisms are necessitated, flow from the cylinder to the accumulatorbeing prohibited through the normally closed check and shutoff valveblock, and flow from the accumulator to the cylinder being prohibitedthrough the normally closed by-pass relief valve block.

In such systems, the shutoff valve delays return of the piston to itsextended position, to aid in stripping parts from the die elements.Thus, accumulator-to-cylinder flow must be completely prevented which,of course, necessitates complete closure of the relief valve during thatinterval. Thereafter, the piston assumes its extended position, followedby actuation of the press to its closed or working position.Subsequently, the piston is forced downward within the cylinder by thepress work stroke to subject hydrualic fluid trapped underneath thepiston to an initial pressure proportional to the working pressure ofthe press.

Initial downward movement of the piston is firmly resisted by theunvented hydraulic fluid trapped between the cylinder and the normallyclosed relief valve before the relief valve opens for venting of thefluid to permit downward displacement of the die pad. High contactpressures are generated between the die elements and within thehydraulic system during this initial unvented interval, thereby inducinga substantial shock load upon the entire press and hydraulic system.This decreases the useful life of the apparatus and increases the costof maintaining it.

Upon opening of the press, pressure differential within the hydraulicsystem causes fluid to return to the cylinder 3,3622% Patented Jan. 9,1968 through the by-pass relief valve to reposition the piston alongwith the die pad in the elevated position preparatory for the nextworking stroke of the press.

The present invention overcomes or substantially alleviates theabove-recited prior art disadvantages by providing an improved hydrauliccontrol system which has a continuously open variable discharge reliefvalve in combination with a hydraulically floating combination check anddelay valve assembly for cushioning the initial closing and subsequentdownward movement of the die elements by accommodating controlledhydraulic fluid flow from the cylinder to the accumulator through thecontinuously open relief valve and a variable volume reservoir duringthat interval of the press operation.

The present invention is easy of initial installation, incurscomparatively low maintenance costs, is simplified in construction andis adaptable to a wide variety of workpieces whereby any set of a seriesof die elements may be utilized.

It is, therefore, a primary object of the present invention to provide anovel control valve assembly for controlling movement of the die pad toand from a working position in a press.

Another object of this invention is the provision of a novel improvedand substantially simplified valve assembly having a flow control valvemechanism such as to cushion initial contact of the die elements and theresulting shock load upon the hydraulic system, thereby alleviating theextremely high initial hydraulic pressure loads encountered at thebeginning of each press work stroke. The flow control valve mechanism ispreferably of unitary construction allowing for easy, unitary removaland replacement according to maintenance requirements.

A further object of the present invention is to provide a novelhydraulically floating combination delay and check valve assembly,hydraulically actuated and providing a common main passage in the valvebody for flow to and from the cylinder and having means for delayingreturn of the piston to the extended position after the press workstroke.

Yet another, and no less important, object is to provide a novelvariable volume reservoir within a main valve body for cushioninginitial contact of the die element and hydraulic shock pressure loads atthe commencement of the press work load and for delaying return of thepiston to its extended position.

Other objects of this invention will become apparent from the followingdescription and appended claims, in conjunction with the accompanyingdrawings, wherein:

FIGURE 1 is a schematic representation of a die pad press controlmechanism, especially illustrating in detail a presently preferredhydraulic control valve assembly of the present invention in a neutralor inactive position;

FIGURE 2 is a fragmentary schematic of the mechanism of FIGURE 1 withthe control valve assembly positioned for cylinder-to-accumulator flow;and

FIGURE 3 is another fragmentary schematic of the mechanism of FIGURE 1with the control valve assembly positioned for accumulator-to-cylinderflow.

GENERAL DESCRIPTION As shown in FIGURE 1, it will be seen that anaccumulator 16 supplies hydraulic fluid to hydraulic line 11 at standardshop air pressure, for example, on the order of to p.s.i., to main valvebody 12, thereafter through hydraulic line 13 into cylinder 14, thehydraulic fluid entering beneath die supporting piston 15.

The hydraulic fluid in cylinder 14 beneath the piston 15 provides acushion to protect the die as the press ram descends. A time delay inreturning piston 15 to its extended position following the work strokeis achieved by a novel assembly within valve body 12 which temporarilyprohibits return of hydraulic fluid to cylinder 14 for the period ofdelay desired. This time delay is integrated with the press operation toaid in stripping pressed workpieces from the die elements. Once thedelay has been achieved, valve body 12 accommodates full flow ofhydraulic fluid from accumulator to cylinder 14, thereby restoringpiston 15 to its elevated position.

Specifically, with reference to the drawing, line 11 supplied fluid tochamber 16 of valve body 12 which is aligned with and opens intocylindrical main valve body bore 17. Additionally, hydraulic line 11supplies fluid to passageways 18, 19 and 20 of valve body 12, passage 20communicating with the medial portion of bore 17.

Another flow path providing fluid communication between line 11 and bore17 is achieved through passages 21 and 22. Retained within passage 21 instationary position is a cylindrical bleed sleeve 23 which receivestherethrough an elongated bleed valve 24. Fluid communication betweenline 11 and passage 22 through passage 21 occurs through an inclinedradial slot 25 of bleed valve 24. Valve 24 is threadedly selectivelyadjustable by exterior handle mechanism 26 to position slot 25 forselectively varying the small amounts of pressured fluid discharged frombore 17 to line 11. Since flow can occur through only that portion ofthe slot 25 exposed beyond the sleeve 23, adjustment of the slot 25axially in the sleeve 23 adjusts the volume flow.

Main body valve bore 17 receives fixed valve sleeve 27 therein, theinterface between bore 17 and the sleeve 27 being sealed by suitablemeans, as by appropriately sized and spaced O-rings (not shown). Sleeve27 has a central bore 28 interrupted by radial passage 29 and annularchamber 30a which establishes communication between the sleeve bore 28and an upper valve block passage 30. A second radial passage 31 is alsoprovided in sleeve 27, together with annular chamber 32, passage 31 andchamber 32 being in constant communication with passage 20. Positionedwithin the sleeve 27 is a reciprocating valve body 34 having main axialflow passage or recess 35 through which fluid flow to and from cylinder14 must pass. Valve body 34 also provides rearward radial passages 36and forward radial passages 37 for fluid communication with passage 35.Radially enlarged piston 38 is carried by and reciprocates with valvebody 34 at its forward end, piston 38 being sealed in chamber 16 bymeans of flexible diaphragm 39 of standard commercial type, thediaphragm 39 engaging the valve block and the piston 38, respectively.Valve body 34- is moved between extreme left and right positions solelyby differential fluid pressure acting thereon as explained hereinafter,no compression springs or other external actuating means being required.

Interposd between movable body 34 and piston 38 is annular insert 40which provides a peripheral valve seat for centrally confined checkvalve 41. Insert 40 moves unitarily with the reciprocating combinationof piston 38 and body 34. Check valve 41 is positioned adjacent theradial flow passage 37 and is urged to its illustrated inactive closedposition by compression spring 42.

As illustrated, bore 17 communicates through passage 44 in the uppervalve block with a continuously open, variable discharge relief valveassembly 46, passage 44 being located at the lefthand end of sleeve 27.Relief valve assembly 46 is interposed between and provides fluidcommunication to passage 44 from passage 48, which communicates withcylinder hydraulic line 13, with upper valve block passage 30 and withpressure gauge 50 through passage 52 and bore 54.

Referring now to the details of relief valve 46, which is preferably aunitary cartridge, there is provided stationary outer sleeve 56 radiallyapertured at 58 into annular chamber 59 to define a stationary per viousportion of the relief valve 46. Chamber 59 facilitates constant opencommunication between passages 48 and 44. Reciprocable valve body ormovable portion 60 of relief valve 46 is axially slidably positioned inbore 62 of sleeve 56 and has a chamfered annular edge 63. Lip 64 ofvalve body 60 is urged against shoulder 66 of stationary sleeve 56 bycompression spring 68 so as to leave apertures 58 at least partiallyopen at all times. Orifice 70 vents fluid from conduit 48 through valvebody 60 to ball check valve 72 which i normally urged to the closedposition by compression spring 74. Check valve 72, when opened, relievesthe pressure on the lefthand side of valve body 60 to accommodateleftward sliding thereof to permit greater discharge through apertures53, thereby cushioning against excessive shock pressure build-up in thehydraulic system. The pressure at which check valve 72 will open isdetermined by the compression of spring 74 which, in turn, is controlledby selectively settable handle 76.

Interposed between handle 76 and unitary cartridge relief valve 46 issupport sleeve 77, attached to the valve body at 79 and to handle 76 at81, as, for example, by threaded connection. This interrelation of partsprovides a significant advantage. When relief valve 46 becomesineffective due to wear or is in need of service, support sleeve 77 maybe conveniently detached from the valve body at connection 79 followedby unitary removal and replacement of the cartridge constituting reliefvalve 46. Performance of this procedure requires only a few seconds oftime and, hence, avoids costly equipment down time.

Disposed in passage 44 between relief valve 46 and bore 17 is checkvalve 80 which accommodates selective fluid flow from passage 48 intochamber 90 and prevents reverse flow from chamber 90 into passage 48.Check valve 80 is housed in sleeve-like seat 86 and urged to its closedposition by compression spring 84. Flow through valve 80 occurs throughradial ports and central bore 87 when spring 84 is compressed due tocylinder pressure from passage 48.

OPERATION In the at rest position, as shown in FIGURE 1 immediatelypreceding the work stroke of the press ram, relief valve 46 is in itsidle partially opened position, check valve 80 is closed, being seatedagainst sleeve 86, and the combination of movable body 34, piston 38 andinsert 40 is in the extreme rightwardmost position. Consequently,passage 30 is in communication with recess 35 of movable body 34 throughradial ports 36. Flow through recess 35 is prevented, since no outletports therefrom are open in this position.

During the work stroke of the piston 15, cylinder-toaccurnulatorhydraulic flow results, the pressure in line 13 being significantlygreater than the pressure of hydraulic fluid within accumulator 10 andline 11. At the making of initial contact between the die elements, thehydraulic fluid in cylinder 14 and line 13 is instantaneously subjectedto a relatively high pressure which is exerted upon the relief valveassembly by passage 48. The shock of this initial hydraulic pressure isinitially alleviated by immediate flow of the pressurized fluid throughcontinuously open apertures 58 of relief valve 46.

If the apertures 58 were closed, the initial shock could be dissipatedonly after fluid flow through the aperture 58 and the actuation of thevalve element 72 to allow movement of the valve body 60. Thus, thedisplacement of valve body 60 would require a period of time duringwhich, in effect, a solid column of hydraulic fluid supports the piston15 and transmits the press shock. However, since the pressure reliefvalve body 60 need not be displaced by the high hydraulic pressures fromline 13 for flow therethrough to occur, an initial small quantity offluid under cylinder pressure flows through apertures 58, displacingcheck valve 80 from its seat and accommodating flow through valve 80 andpassage 44 into bore 17 to thereby cushion the initial shock of thedies, aid materially in prolonging the useful life of the pressassembly, and provide a significantly improved, i.e., smoother, pressoperation.

At and immediately following initial contact of the die elements, thepress ram forces the piston 15 downwardly, further increasing thepressure in line 13 and passage 48. This pressured fluid flows throughorifice 70 to lift ball 72 from its seat, allowing relief valve body 60to move to the left against the force of spring 68 to increase dischargeof fluid through ports 58 and passage 44 into bore 17.

Under cylinder pressure, fluid initially passing through the passage 44into bore 17 accumulates in the variable volume annular reservoir orchamber 90, thereby exerting pressure upon the righthand face of thepiston 38 to unitarily drive piston 38, insert 40 and movable valve body34 leftward, as viewed in FIGURE 1. This causes movable body 34 tounseat from the fixed sleeve 27 at 92, permitting fluid to flow from thereservoir 90 through passages 37 into the axial recess 35. Reservoir 90is progressively enlarged as more fluid under cylinder pressure isreceived through passage 44, while movable body 34, piston 38 and insert40 continue to move leftward. By this progressively enlarging storagecapacity for hydraulic fluid in reservoir 90, excessive cylinderpressure buildup is further alleviated.

While the size of reservoir 90 is progressively enlarging, fluid storedin reservoir 90, recess 35 and valve passage 22 is vented throughbleed-valve slot 25 to provide a controlled small discharge into line11, according to the setting of bleed-valve handle 26, therebyregulating the initial rate of downward movement of piston 15.

When valve body 34 has completed its leftward movement, so that the leftend of the piston 38 abuts the end of chamber 16, as seen in FIGURE 2,reservoir 90 is enlarged to its maximum volume. In this position,maximum flow communication is established from reservoir 90 and recess35 through passages 36, annular chamber 32 and passages 31, 20, 19 and18 to hydraulic line 11. This accommodates downward movement of thepress ram and die pad during the work stroke. As the ram and die paddescend, maximum flow of the fluid from the cylinder to the accumulatorcontinues through line 13, passage 48, relief valve 46, check valve 80,reservoir 90, passage 37, recess 35, passage 36, chamber 32, passages31, 20, 19, and 18 and line 11 (see FIGURE 2).

Maximum flow accommodates steady downward movement of piston 15 withincylinder 14 as the press stroke continues. When the press stroke hasbeen completed, pressure within line 13 drops to substantially zero, andrelief valve 46 returns to its initial at rest, partially open position.At this time, the press stroke is completed.

It is now necessary to elevate the piston 15 for the next press stroke.Check valve 80 closes against seat 86 to prevent accumulator-to-cylinderflow. Unitary reciprocable elements 38, 4t) and 34 move to the rightbraking communication between radial passages 36 and valve body passage20, thereby trapping a measure of buffer hydraulic fluid in thereservoir 90, in the axial recess 35 of movable valve body 34 and in thepassage 22, as fluid under accumulator pressure flows from conduit 11into chamber 16. Fluid thus entrapped within reservoir 90, axial recess35 and passage 22 is under a pressure greater than the accumulatorpressure, which greater pressure acts upon the face 96 of check valve 41to hold the check valve closed as elements 38, 40 and 34 move rightward.

Thus, at this juncture, there will be no flow from line 11 to line 13,members 38, 40 and 34 being positioned between their extreme left andright positions and moving relatively slowly toward the right, as viewedin the figures. The fluid entrapped in chamber 90 between piston 38 andfixed sleeve 27 and also within recess 35 resists such movementaccording to the amount of fluid escaping therefrom through sleeve slot25 of the bleed valve 24. The adjustment of handle 26 will axiallyposition bleed valve 24 with respect to bleed valve sleeve 23 and willtherefore determine the time necessary before flow is elfectuatedbetween lines 11 and 13 and, accordingly, the amount of time delayfollowing the press work stroke before the piston commences upwardmovement toward its extended position. This time delay accommodates easeof stripping the fabricated workpiece from the die elements.

Once the valve body 34 has moved rightward to an extent such that radialpassages 36 are brought into communication with chamber 30a and passages29 and 30, fluid entrapped in reservoir and passages 35 and 22 willescape to line 13 by this route. Until then, the above described delaymechanism entirely prohibits escape of any fluid into piston conduit 13.After this condition has been obtained, valve body 34 moves swiftly witha snap action to its extreme rightward position causing body 34 to againseat against sleeve 27 at 92.

Once the entrapped fluid in reservoir 90 and passages 35 and 22 escapesthrough passage 30 to line 13, accumulator pressure acting upon face 98of check valve 41 overcomes the resistance of spring 42, causing checkvalve 41 to open, as illustrated in FIGURE 3. Thereafter, hydraulicfluid freely flows at accumulator pressure through check valve 41, axialrecess 35, radial passages 36, passages 30 and 48, line 13, intocylinder 14, to cause piston 15 to return to its extended position.

Thus, the present invention provides a hydraulic control systemintermediate an accumulator and a press responsive piston, being ofsimplified construction and improved operation. A continuously open,variable discharge, relief valve (located on the cylinder side of themain valve body) is utilized in conjunction with a hydraulicallyfloating combination delay and check valve assembly (which ishydraulically responsive) to provide a common flow path to and from thecylinder and permitting (through the relief valve) initial indirect flowbetween the cylinder and the accumulator through a progressivelyenlargeable hydraulic fluid storage reservoir, so as to alleviate theshock load induced by the high initial cylinder pressure upon thehydraulic system and upon the die elements. The relief valve ispreferably a unitary cartridge accommodating easy, unitary removal andreplacement, thereby requiring essentially no special equipment or downtime for the exchange. The variable capacity hydraulic fluid storagereservoir, in conjunction with the continuously open variable dischargerelief valve, provides a graduated cushioning effect permitting smoothoperation of the press mechanism during the working stroke. The floatingcombination delay and check valve also facilitates return flow from theaccumulator to the cylinder by providing a progressively decreasingstorage volume of trapped hydraulic fluid in the reservoir which isslowly discharged therefrom into the accumulator conduit for acon-trolled duration of time to delay return of the piston to itsextended initial position, facilitating separation of the workpiece fromthe die elements. This operation prohibits entry of hydraulic fluid intothe cylinder conduit during the delay action and, consequently, thepiston remains in its fully retracted position during the delay forimproved stripping of parts being fabricated,

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the inventionrbeing indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a ram-type press wherein a die pad engages the work and isretracted upon the closing of the press ram, a hydraulic cylinder andpiston reacting upon said die pad to resist such movement and to returnthe die pad to its extended position after opening of the press ram, anaccumulator tank of hydraulic fluid under relatively loW pressure,hydraulic fluid flow and pressure transmitting connections between saidtank and cylinder for supplying hydraulic fluid under tank pressure tothe cylinder when the tank pressure exceeds that of the cylinder, andcontinuously open valve means disposed in said hydraulic connections andaccommodating the flow of fluid from said cylinder so as to cushion theshock load of hydraulic fluid from said cylinder during closing of thepress ram, said valve means comprises a continuously open relief valvehaving a stationary pervious portion and a movable portion thereofhaving hydraulic pressure responsive surfaces to cause said movableportion to move relative to said stationary portion in response topressure differential to thereby permit increased fluid flow throughsaid relief valve following closing of the press during the work strokethereof.

2. A device as defined in claim 1 further including a selectivelysettable means for varying the degree of resistance afforded againstsaid relative movement of said movable portion with respect to saidstationary portion of said continuously open relief valve.

3. A valve mechanism for controlling the flow of hydraulic fluid betweenan accumulator and a cylinder contained pressure-actuated die pad pistoncushion, comprising a main valve body interposed between saidaccumulator and said cylinder, fluid means connecting said main valvebody to said accumulator and said cylinder, respectively, and pressureresponsive delay and check combination valve means biased betweenextreme positions in said main valve body solely by differential fluidpressure exerted thereon so as to permit fluid flow to and from saidcylinder through a common main flow passageway having a plurality ofingress and egress fluid passageways, to provide a time delay betweenthe completion of the piston work stroke and return of the piston to itsextended position to its extended position thereafter.

4. A device as defined in claim 3 wherein said delay and checkcombination valve means includes reciprocating body means and springbiased check means carried by and normally unitarily movable with saidbody means so as to prevent cylinder to accumulator flow through saidcheck means and to accommodate accumulator to cylinder flow therethroughwhen said check means is acted upon solely by fluid under accumulatorpressure and by said spring bias.

5. A device as defined in claim 3 further including a stationary sleevemeans interposed between said main valve body and said delay and checkvalve means accommodating reciprocal movement thereof, providing avariable volume hydraulic fluid reservoir therebetween and having fluidingress and egress means such that fluid under piston pressure willcause said variable volume reservoir to progressively enlarge therebyalleviating shock load induced by cylinder pressure initiated by thecommencement of the press work stroke and capable of entrapping fluid insaid variable volume reservoir at the completion of said work stroke anddischarging said entrapped fluid at a slow controlled rate toprogressively decrease the volume of said chamber to thereby delayreturn of said piston to its extended position.

6. A device as defined in claim 5 having selectively settable means forvarying the rate of discharge of said entrapped fluid.

7. In a hydraulic system of the type described for controlling themovement of a die or like press including piston-containing cylindermeans, accumulator means and main valve body means interconnected byappropriate fluid conveying passageways, the improvement comprisingcontinuously open relief valve means within said main valve body meansenabling controlled initial cylinder-toaccumulator flow at thecommencement of the press working stroke upon the piston to cushionagainst high initial pressure build-up and resulting shock loads upondie elements and upon the hydraulic system, said valve means comprisinga fixed apertured sleeve and a movable portion guided by said sleeve andhaving a first extreme position wherein a portion of the apertures ofsaid sleeve are uncovered and a second extreme position wherein theentire apertures are uncovered.

8. A valve mechanism for controlling the flow of hydraulic fluid betweenthe accumulator and a press-actuator die pad cushion carried by a pistoncontaining cylinder, comprising a main valve body interposed betweensaid accumulator and said cylinder, fluid means connecting said mainvalve body to said accumulator and said cylinder, and pressureresponsive combination delay and check valve means reciprocally biasedbetween extreme positions, said delay and check valve means includingmeans providing a variable volume cushioning reservoir for hydraulicfluid under accumulator pressure to thereby alleviate shock loadsnormally initiated at the commencement of the press work stroke,controlled reservoir discharge means for delaying return of the pistonto its extended position following the press work stroke, meansaccommodating cylinder-to-accumulator hydraulic fluid flow during alatter interval of the press work stroke, and means accommodatingaccumulator-to-cylinder hydraulic fluid flow during an interval of theperiod wherein said piston is resuming its extended position.

9. A device as defined in claim 8 and further including pressure reliefvalve means situated within said main valve body on the inlet side ofsaid delay and check valve means when fluid is flowing from the cylinderto the accumulator, said discharge means including a bleed valve andbleed passage located between said pressure relief valve means and saidaccumulator on the outlet side of said pressure relief valve means.

10. In a valve mechanism for controlling the flow of hydraulic fluidbetween an accumulator and a cylinder contained pressure-actuated diepad piston cushion, comprising a main valve body interposed between saidaccumulator and said cylinder, fluid means connecting said main valvebody to said accumulator and said cylinder, the improvement comprisingpressure responsive hydraulically delay-check combination valve meansbiased between extreme positions in said main valve body solely bydifferential fluid pressure exerted thereon so as to permit fluid flowto and from said cylinder through a common main flow passageway whichhas a plurality of ingress and egress fluid passageways and to cushionagainst excessive cylinder pressure loads and to provide a time delaybetween the completion of the piston work stroke and return of thepiston to its extended position thereafter, and continuously open reliefvalve means disposed in said main valve body on the cylinder sidethereof so as to cushion against excessively high pressure build'up byenabling a controlled initial discharge of hydraulic fluid from saidcylinder through the continuously open relief valve means into the delaycheck combination valve means during closing and initial work movementof the press ram.

11. In a ram-type press, wherein a die pad engages the work and isretracted upon the closing of the press ram, having a hydraulic cylinderand piston reacting upon said die pad to resist such movement and toreturn the die pad to its extended position after opening of the ressram, an accumulator tank of hydraulic fluid under relatively lowpressure, and hydraulic fluid flow and pressure transmitting connectionmeans between said tank and cylinder for supplying hydraulic fluid underpressure to the cylinder when the tank pressure exceeds that of thecylinder and for supplying hydraulic fluid under cylinder pressure whenthe cylinder pressure exceeds the tank pressure, the improvementcomprising a continuously open valve assembly means disposed in saidhydraulic connection means and accommodating the flow of fluid from saidcylinder so as to cushion the shock load of hydraulic fluid from saidcylinder during closing of the press ram, said continuously open valveassembly means comprising stationary means, means movable relative tosaid stationary means, said movable means being biased in said firstextreme position to accommodate limited flow between the cylinder andaccumulator, and means for creating a pressure differential on oppositesides of said movable means to move said movable means toward a secondextreme position when the cylinder pressure exceeds the tank pressure,said stationary and movable means combining to provide continuously openfluid communication opening means having flow capacity varying with theposition of said movable means.

12. The improvement as defined in claim 11 further including a checkvalve means within said hydraulic connection means intermediate saidaccumulator tank and said continuously open valve assembly meansaccommodating cylinder-to-accumulator flow while preventingaccumulator-to-cylindner flow through said check valve means and saidcontinuously open valve assembly means.

13. In a ram-type press having a hydraulic cylinder and piston, anaccumulator, and fluid connection means between said cylinder and saidaccumulator, the improvement comprising a valve mechanism disposedwithin said fluid connecting means for accommodatingcylinder-toaccumulator flow of hydraulic fluid and for controlling theflow of hydraulic fluid between the accumulator and the cylinder, saidvalve mechanism comprising in combination a pressure responsive delayvalve means to provide a time delay between the completion of the pistonwork stroke and the return of the piston to its extended positionthereafter and check valve means carried by and forming part of saiddelay valve means, said check valve means being movable between anormally closed position and at least one open position by pressuredilferential on 10 opposite sides thereof, said check valve meansaccommodating fluid flow from said cylindner across one said oppositeside and to said cylinder across at least the other of said opposideside.

14. In a ram-type press wherein a die pad engages the work and isretracted upon the closing of the press ram, a hydraulic cylinder andpiston reacting upon said die pad to resist such movement and to returnthe die pad to its extended position after opening of the press ram, anaccumulator tank of hydraulic fluid under relatively low pressure,hydraulic fluid flow and pressure transmitting connections between saidtank and said cylinder for supplying hydraulic fluid under tank pressureto the cylinder when the tank pressure exceeds that of the cylinder, acontinuously opened, unit relief valve disposed in said hydraulicconnections and continuously accommodating flow of fluid from saidcylinder so as to cushion the shock load of hydraulic fluid from saidcylinder during closing of the press ram, and removable meanspositioning said unit relief valve in said hydraulic connections andaccommodating unitary removal and replacement of the unit relief valvetherefrom with essentially no press down time.

References Cited UNITED STATES PATENTS Re. 25,027 8/ 1961 Williamson2671 2,890,669 6/1959 Williamson 267-1 3,124,343 3/1964 Williamson 267-13,147,962 9/1964 Williamson 267-1 3,251,214 5/1966 Williamson 723513,267,715 8/1966 Williamson 72-351 3,268,220 8/ 1966 Williamson 26713,279,780 10/1966 Williamson 267--l CHARLES W. LANHAM, Primary Examiner.A. RUDERMAN, Assistant Examiner.

